> Predatory behavior and top-down effects in marine ecosystems are well-described, however, intraguild interactions among co-occurring marine top predators remain less understood, but can have far reaching ecological implications. Killer whales and white sharks are prominent upper trophic level predators with highly-overlapping niches, yet their ecological interactions and subsequent effects have remained obscure. Using long-term electronic tagging and survey data we reveal rare and cryptic interactions between these predators at a shared foraging site, Southeast Farallon Island (SEFI). In multiple instances, brief visits from killer whales displaced white sharks from SEFI, disrupting shark feeding behavior for extended periods at this aggregation site. As a result, annual predations of pinnipeds by white sharks at SEFI were negatively correlated with close encounters with killer whales. Tagged white sharks relocated to other aggregation sites, creating detectable increases in white shark density at Ano Nuevo Island. This work highlights the importance of risk effects and intraguild relationships among top ocean predators and the value of long-term data sets revealing these consequential, albeit infrequent, ecological interactions.
I only skimmed it, but it doesn't seem that they looked directly at whether the sharks actually fear Orcas per se. It is already known that white sharks flee whenever one of their own is killed by anything, which they can smell from some distance away. They remember to avoid that area for some time afterwards.
"Great White Sharks are terrified of Orcas" suggests a higher level of intelligence than "Great White Sharks evolved to fear anything that can kill a Great White Shark".
It seems that the study is less concerned with that mechanism and more with the fact that this kind of displacement leads to White Sharks occupying sub-optimal hunting grounds while Orcas get to go wherever they want.
The article says that even if orcas pass through an area where the sharks are hunting, the sharks will leave the area and not return for months. It does not mention any sharks being killed.
Is that that different from human fears? We’ve presumably also evolved to be instinctually afraid of categories of things capable of harming or killing us, like snakes and spiders. Our intelligence lets us more carefully sub-categorize these into things that actually can kill us (Black Widows and Cobras) from things that can’t (Orb Weavers and Rat Snakes). Even then though, running across a big shiny Orb Weaver or Rat Snake in the wild shakes loose something deep in your brain telling you to stay away.
> It is already known that white sharks flee whenever one of their own is killed by anything
But white sharks fight each other, kill each other and even eat each other on occasion. We know that white sharks fetuses cannibalize each other in the womb. How could they do that if white shark blood scares them off? Also, is there really a difference in smell between white sharks and other sharks, seals, etc?
This is such an easy thing to test. Has anyone taken white shark blood and tested it on white sharks ( captive or wild )? Also, does this only work on white sharks? Do tiger sharks, nurse sharks and other sharks fear blood of their own species?
Finally, white sharks are scavengers as well as hunters ( like most predators ). As far as I know, every scavenger will cannibalize when given the chance. Are white sharks the exception?
Also, most animals flee when they see, smell or hear a predator. So I think it's most likely that white sharks flee when they sense a potential predator.
If truly shark blood scares off sharks, then coast guards should dump some shark blood near beaches where sharks frequent.
Hollywood/Spielberg promoted the fantasy that sharks are predatory to humans, where we are more often mistaken for seals and other natural shark prey when out in the water. An acquaintance recently told me he was surfing at Salmon Creek a couple of weeks ago and a great white hit him on the back of his head with a powerful flick of his tail while he was laying prone on his longboard, a wave came along almost immediately after this and took him shore wards (still prone). This was almost certainly a 'seal slap' stun move, sharks don't do anything by accident. My friend then saw another surfer on his way in paddling out who saw the shark silhouette in the wave and headed back to the beach. It's scary but there are very few actual shark bites and kills of humans despite the terror film sell, but it is still a mystery how we can discourage them from the coastal beach waves where they have every right to be.
Despite dolphin's adorable perception by humans you can see them torturing and raping seals in the San Francisco bay, it's a jungle out there...
Oceanic white tips and Tiger Sharks are man eaters, they have been know to stalk, hunt and consume humans. They will return to devour a human. The meme that Sharks do not eat humans is not entirely true, but the reality is they prefer other meals. Well at least the tiger shark does. Oceanic white tips are the piranhas of the open ocean, they eat everything they come across. It is a good thing they only live in open ocean as if they where a shallow water shark there would be far more shark attacks.
I spearfish, and have spent a lot of time in the water with sharks. There nature is very much like that of dogs. If you show fear, try to flee and basically make yourself look like prey they will get attracted. If you stand your ground, give them a nudge to the face when they get to close. They see you as a competing apex predator that can hurt them, sharks are adverse to fighting for their meal. It is why injured fish is such and attraction to them. I have been in the water with them, just cruising around not paying any attention to anything, someone shoots a fish and all hell breaks loose if you don;t get the fish up fast enough. Once you are in possession of the fish they act as if another shark got it and go back to just cruising around. If they get to your fish before you get it up, they will clean it off the spear in seconds flat.
In my few encounters, Sharks tend to avoid any dolphin species including porpoises and Bottle-nose. In the presence of humans it has been my experience that dolphins tend to be more aggressive towards sharks, running them off. I don't read too much into it, because I imagine they probably do the same when we are not around.
I would imagine that sharks compete for the same food source so they run them off to ensure food availability. Dolphins will also not try to steal your catch, at least not in my experience.
My expereince with dolphins is limited though, I have only been in a pod while spearfishing twice and both times where due to the fact that there was a bait ball, so there where a lot of predators competing for prey fish. Including Sailfish and Marlin, which the dolphins seem to use as the billfish bat thru the ball stun the fish and then the pod will grab some of the stunned fish.
My personal experience is that dolphins know what spearguns are, and don't like them, they generally don't approach if you are spearfishing. The release of a spearshaft and the band pop is a very distinct vibration, many apex fish including large grouper and sharks are keyed into it, in some areas. I remember one time, I pulled the trigger and had two blacktips on me within a split second. The fish was dead on impact so the only vibration was the gun going off. Anyways I would guess that dolphins key into this as well and avoid it.
That being said, when I am in the water without a gun they always approach check me out, push their babies towards me to check me out. I think it's akin to us going to sea world, it really is like hey kids look it's a human check it out, get a good look you don't get to see these too often.
One time my dog jumped in and the babies would swim about a foot under it, to make it go crazy barking. I think they loved the sound as when she would stop they would circle back and get her going again. (Side note: I think dolphins are into ASMR if you are ever in the water with them make sounds they love it). It was the one time I thought to myself, I hope dolphins don't eat dogs because she is a beagle, so small enough. Anyways, they don't, and I am glad they don't hunt humans, if they did we would not be able to enter the water. A human hunting dolphin would be a fearsome predator and absolutely terrifying in a serial killer kind of way. They are really smart and you get a feel for how smart they are when you have natural encounters with them.
The most common projection from the mouse retina is actually a highly-specialized and evolutionarily-conserved hawk detector. It responds to dark, looming stimuli against bright or grey backgrounds.
I am all for pairing naturalistic observations with more controlled experiments. However, actively harassing adult great white sharks would be one hell of a thesis project.
Abstract:
> Predatory behavior and top-down effects in marine ecosystems are well-described, however, intraguild interactions among co-occurring marine top predators remain less understood, but can have far reaching ecological implications. Killer whales and white sharks are prominent upper trophic level predators with highly-overlapping niches, yet their ecological interactions and subsequent effects have remained obscure. Using long-term electronic tagging and survey data we reveal rare and cryptic interactions between these predators at a shared foraging site, Southeast Farallon Island (SEFI). In multiple instances, brief visits from killer whales displaced white sharks from SEFI, disrupting shark feeding behavior for extended periods at this aggregation site. As a result, annual predations of pinnipeds by white sharks at SEFI were negatively correlated with close encounters with killer whales. Tagged white sharks relocated to other aggregation sites, creating detectable increases in white shark density at Ano Nuevo Island. This work highlights the importance of risk effects and intraguild relationships among top ocean predators and the value of long-term data sets revealing these consequential, albeit infrequent, ecological interactions.